I've got the Edelbrock dual quad intake manifold and twin Edelbrock 500 cfm carbs on my lil' 306. I haven't yet dynoed it, but plan to do so within the next month or so. I'm guessing that I have 320-330 rear wheel horsepower. Time will tell if I'm in the ballpark.
It runs great! I've run a best of 12.88 @ 110 (on E.T. Streets) with very little seat time at the track. I'm still a rookie when it comes to launching so my '60 foot times weren't the greatest. As for the street, it's very streetable. It idles at 1,000-1,100 rpms and never loads up or floods out (I drive it to work 2-3 days per week.) We bought the Edelbrock calibration kits and have used them to the best of our ability to tune it. The dyno should allow us to fine tune it some more.
I know that I can make more power with a Victor Jr. intake manifold and a 750 cfm carb, but I like the fact that I have a different look when I open my hood. I'm willing to sacrifice 20+ horsepower just for the response that I get when I attend a cruise night or a car show.
If you want to use a setup like this, I suggest 9:5:1-10:5:1 compression ratio or higher (I have 10:8:1,) a high lift cam, aluminum heads (or cast iron GT 40's/'69-'70 351W, ported and polished of course) and long tube headers. It will be a high revving engine (shifting can be done @ 6,500+ rpms!) Of course, you'll need the required transmission/rearend setup to go along with it. Here's a pic of mine.